Getting Weatherwise – AMC Outdoors

January 8, 2004

AMC Outdoors, July/August 2002

By Michael Lanza

My buddy Gerry and I were roped together high up in the Tetons, basking in the view and the climbing and thinking the world was our oyster when the first hint of trouble appeared: tentacles of cloud curling around higher summits nearby. Within 20 minutes, the sky transformed into a seething, gray-black river of water vapor moving like a Class V rapid. Lightning flashes lit up everything around us; I felt each thunderclap in my ribs. Hail and rain sprayed the cliff as if fired from an automatic weapon.

I stood on a ledge the width of my foot as water streamed down the cliff and heard a noise I’d never heard before — inexplicably, coming from right behind me. Startled, I spun my head around and saw, of course, nothing but storm-lashed mountains. But when I turned back to the cliff and the pressing business of getting out of there, I heard the noise again and realized with a sickening feeling what it was: the ice axe on my pack, which we’d needed for the snow couloir on the approach and descent, was humming like a tuning fork in the charged air. The rest of the tale is too long to elaborate on here (and something for which I usually charge one beer), but suffice it to say that Gerry and I got off that mountain unharmed — and our hair eventually stopped standing upright. But on our way down we came upon the body of a climber who did not fare so well. We later learned he’d fallen 500 feet trying to make a hasty retreat; he was a disturbingly vivid image of the dangers of bad weather when we play outdoors.

You don’t have to be a climber to get on Mother Nature’s bad side. She offers equal opportunity for the most frightening experience of your life — and possibly the last experience of your life — to hikers and backpackers; to boaters on rivers, lakes, and the ocean; and to anyone venturing into the mountains on snowshoes, skis, or crampons. She seems to draw particular pleasure from sapping the enthusiasm of outdoor enthusiasts in the Northeast, where the confluence of mountains, ocean, and colliding weather systems keeps things interesting. Knowing a little bit about how to read the skies and anticipate an approaching storm early enough to escape it is the best way to avoid her wrath.

Signs in the SkyCloud formation is the obvious signal of weather moving in, but different clouds foretell different developments. Watch for some of the following warning signs.

White, puffy cumulus, or “fair-weather,” clouds, don’t always bring foul weather, but when they start to thicken, showers may soon follow. When small cumulus clouds in the mountains become larger and cauliflower-like, heavy rain or snow, gusty winds, and possibly thunder and lightning will probably follow within an hour. If the sharp edges of cauliflower cumulus soften at their outline, ice crystals are forming and are likely to be followed by thunder and lightning.

Wispy, high cirrus clouds, or “mare’s tails,” usually arrive about 24 hours in advance of a warm front bringing rain or snow.

A halo, or wide ring, around the sun or moon means rain or snow is likely within 24 to 48 hours. Similarly, a corona, or close ring, around the sun or moon means rain or snow to follow within 12 to 24 hours.

Lenticular or “cap” clouds, which look like a giant inverted bowl or alien spacecraft, form over peaks — often above the highest mountains in the immediate area. They indicate strong winds on the summit and forebode rain within 48 hours.

Technology can lend a hand in reading the skies. An altimeter calculates your altitude by reading the barometric pressure at your location, which also makes it helpful in forecasting weather. If your altimeter reading goes up when you have not changed altitude — for instance, if you notice a change between when you went to sleep and when you awoke in the same campsite — the barometric pressure has dropped, meaning a storm is approaching.

Similarly, if your altimeter reading drops when you have not changed altitude, the barometric pressure is rising and the weather is likely to improve. Calibrate it — reset it to the correct altitude — anytime you reach a known elevation such as a summit or a trailhead. But don’t rely solely on your altimeter to forecast weather.

If the Thunder Don’t Getcha…While death or injury from lightning strikes is rare, they pose a serious danger for anyone high on a mountain and are very frightening. It’s impossible to predict where or when lightning will strike. While 80 percent of victims survive, one in four suffers major long-term health problems.

The trick is to recognize an approaching thunderstorm before it’s upon you, and gauge how much time you have to get to safer ground.

Afternoon thunderstorms are common in many mountain ranges during summer — especially in mountains with lots of barren terrain, which heats up under the sun much faster than tree-covered terrain, creating rising thermals of warm air that carry moisture upward to form thunderheads. This is frequently compounded by winds hitting the mountains from one direction and flowing upward, called an “orographic effect.”

The ocean and big lakes create a similar thunderstorm effect because water cools more slowly than land; by late morning, sea breezes start blowing inland as the warmer air over land rises and cooler ocean air moves in, forming a “front,” or boundary between warm and cold air masses, where thunderstorms develop.

While thunderstorms in bigger western mountains can seem more intense than those we get in the Northeast, our region’s alpine peaks are dangerous places to be when lightning’s flashing.

An approaching thunderstorm may first appear as a line of dark clouds on the horizon, as clouds rapidly expanding upward and becoming taller than they are long, or as a classic anvil-shaped cloud. Lightning becomes visible when the storm is within about 15 miles; if you can hear the thunder, the storm is probably no more than six to 10 miles away. But terrain and other noise may prevent you from hearing a storm’s thunder or seeing lightning until the storm is within a few miles. A sudden gust of wind often comes up in advance of the front, sometimes just minutes before it hits.

To measure a storm’s distance from you, count the seconds between the flash of lightning and the rumble of thunder that follows it. The sound takes about five seconds to travel a mile, so if you count 10 seconds between the lightning and the thunder, the storm is about two miles off. What to do? When lightning threatens, reduce your risk of being struck. The high-risk factors are standing out in the open; being near a tall, isolated object like a solitary tree; being near or on water; and being near or holding metal objects. If you can’t get out of the open, crouch down with your feet close together and your hands over your ears to protect them from loud nearby thunder.

Contrary to popular belief, there’s no proof that standing on a foam pad, a pack, or anything else will protect you from lightning traveling along the ground. Spread a group out to reduce the risk of multiple casualties, keeping at least 15 feet between any two people. If you hear a buzzing noise, feel a tingling sensation, your hair stands up, or you see a bluish glow around people or rocks, get out of there as quickly as possible.

Finally, don’t embark on any adventure without the conscious realization that you might have to change your plans somewhere along the line if the weather doesn’t cooperate. A lot of people who get into trouble with Mother Nature simply ignore her worsening mood for too long before deciding to change course.

—Michael Lanza is author of The Ultimate Guide to Backcountry Travel, from AMC Books.